Java should install automatically. If it didn't — open Terminal and type "java"

If the system tells you that dmg file is damaged, you need to go to System Preferences > Security & Privacy > General and switch "Allow apps downloaded from" to "Anywhere". You can switch that back after the game is installed.

Linux

hearthlands_1_1_3.tag.gz contains hearthlands.sh, which you can use to launch the game

If you have troubles launching Hearthlands, please send us your system configuration, log.txt file (located in the game directory) and other details, so we can figure out what's wrong.